Drumhead for end sealed cartons and method of making the same

ABSTRACT

This disclosure is directed to an improved method of construction of drumhead type cartons (i.e., parallelepiped cartons whose ends are sealed by independent, taut membranes) in which a fillet means of hot melt material having a generally right triangular cross section is deposited along that portion of the manufacturer&#39;&#39;s joint which extends into the carton dust flaps to provide an uninterrupted peripheral surface to which the membrane ma be tightly adhered. Absolute tightness at the joint is enhanced by simultaneously cross-crushing and cross-sealing the membrane, fillet, and underlying flap portions by a specially configured sealing platen.

United. States Patent Giuliani 15] 3,656,682 [451 Apr. 18, 1972 [s41 DRUMHEAD FOR END SEALED CARTONS AND METHOD OF MAKING THE SAME [72] Inventor: Lawrence E. Giuliani, Rockford, Ill.

[73] Assignee: Riegel Paper Corporation, New York,

[22] Filed: Oct. 1, 1970 [21] App1.No.: 77,231

' [52] 11.5. C1 .229/37 R, 229/14 R, 229/48 T,

511 m0 ..B65d 5/08 581 FieldoiSeai-ch ..53/14;229/37,48SA,48T, 229/1412 [56] References Cited UNITED STATES PATENTS 2,417,104 3/1947 Cope ..229/37 R 3,288,345 11/1966 Dilot ..229/37 R X 3,481,527 12/1969. Jacke ..2 29/37 R 3,580,483 5/1971 Young Primary Examiner-Donald F. Norton Attorney-Mandeville and Schweitzer s7 ABSTRACT This disclosure is directed to an improved method of construction of drumhead type cartons (i.e., parallelepiped canons whose ends are sealed by independent, taut membranes) in which a fillet means of hot melt material having a generally right triangular cross section is deposited along that portion of the manufacturers joint which extends into the carton dust flaps to provide an uninterrupted peripheral surface to which the membrane ma be tightlyadhered. Absolute tightness at the joint is enhanced by simultaneously cross-crushing and cross-sealing the'membrane, fillet, and underlying flap portions by a specially configured sealing platen.

5 Claims, 6 Drawing Figures PATENTEDAPR 181972 3; 656,682

- SHEEI 1 CF 2 INVENTOR. LAWRENCE E. GIULIANI ATTORNEYS PAIENTEDIPR I 8 W2 SHEET 2 UF 2 INVENTOR LAWRENCE E. GIULIANI BY i 2 I ATTORNEYS DRUMHEAD FOR END SEALED CARTONS AND METHOD OF MAKING THE SAME BACKGROUND OF THE INVENTION Many airtight, siftproof, and moistureproof paperboard carton constructions-for liquid and pulverulent materials are formed from parallelepiped cartons and have their opposite ends sealed by safety shield members or drumhead membranes adhered to the carton end flaps and side flaps (dust flaps). Presently, in commercially useful drumhead cartons,

the membrane material and/or the inner surfaces of the flaps to which the membranes are adhered are thermoplastic. For example, a resin, wax or other material which may be easily heat sealed may be coated on the membrane or flaps. The

strength of these drumhead cartons is often custom tailored to meet packaging requirements by the choice of laminated materials used to construct-the blanks. Moreover,with the development of improved coated and laminated paperboard materials and improved thermoplastic films, the tightness and imperviousness of membrane sealed cartons of the aforementioned type have been greatly improved, and these cartons have continued to find ever increasing acceptance and widespread use in diverse packaging applications.

It is to a further improvement in the airtightness or siftproofness of the attachment of the drumhead to the end carton flaps that the present invention is directed. More specifically, where the cartonto be sealed includes a manufacturers joint extending into its dust flaps, it is often possible for the applied membrane to stretch over the right angular step defined step forms a small gap or channel and prevents an e'ndsealed carton from being hermetically or otherwise completely tightly sealed. A proposed solution to this problem has been to form the channel and thereafter (after membrane attachment) to score the membrane and end flap transversely of the manu- For a better understanding of the present invention and its attendant advantages, reference should be made to the following detailed description taken in conjunction with the accompanying drawings; 1

DESCRIPTION or DRAWINGS FIG. 1 is a perspective view of one end of a drumhead carton just prior to sealing of the membrane to the carton end flaps. 1

FIG. 2 is a fragmentary, cross-sectional viewof the drumhead taken along line 2--2 of FIG. 1.

FIG. 3 is'a perspective view schematically showing cartons being advanced along a horizontal path by 'a packaging machine and being glued, taped, and sealed during such advance.

FIG. 4 is a perspective view of one end of the carton after the latter has been taped and completely sealed.

FIG. 5 is an enlarged fragmentary cross-section taken substantially along the line 5--5 of FIG. 4.

FIG. 6 is a fragmentary perspective view 'of the underside of a sealing shoe for sealing the cartons shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, a typical drumheadcarton 10 (of which only one end is shown, it being understood that the opposite end is a mirror image of the illustrated end) includes'a first side wall 11, a rear wall 12, a second side wall 13, a front wall l4, and a glue'flap l5, consecutively articulated along parallel vertical creases 16. The glue flap 15 extends for the entire depth of the carton and above the upper carton edge 17 as a glue flap segment 18. Front and rear carton closing fiaps l9 and 20 are articulated to the front and rear walls at the carton edges 17, as shown, and dust fiaps 21 and 22 are similarly articulated to the carton side walls at the end edges 17 thereof. As showmthe manufacturers joint 30 is formed by adhering the glue flap 15 to the first side wall 11 and by adhering the glue flap segment 18 to'the dust flap2l. As will beapfacturer's joint in orderto eliminate the channel at the site of predated, the glue p g t 18 and dust p 21 the line score. While the score did not eliminate the channel, it sought to cut off communication between the inside of the carton and the carton exterior through the portions of the channel which remained. It is to this specific problem area of drumhead carton formation that the present invention is directed.

- SUMMARY OF THE INVENTION In the present invention, an uninterrupted and continuous bonding surface for the membrane is provided at the carton end flaps, that is, all bonding surfaces are free of steps. Of course, there are no problems in adhering the-drumhead membrane to those carton flaps which are comprised of a single planar surface, those flaps which are not compound flaps.

Rather, the problem is introduced in a compound flap, i.e., the flap containing the manufacturers joint where there is a compound surface made up of an underlying flap and overlying glue segment.

More specifically and in accordance with the principlesof the present invention, a fillet having a sloped surface is formed in situ at the right angular step defined by the edge of the manufacturers joint. This fillet completely fills the step and is in the form of a thermoplastic material, such as a hot melt material commonly employed in packaging applications.

Thereafter, the step is eliminated completely by crosscrushing (cross scoring) during heat sealing.

As will be appreciated, a membrane placed over the open flaps of a carton end may be effectively heat sealed along the entire extent of each of the flaps, since the surfaces thereof are together form a compound dust flap 31 having a generally angular step 32 (see FIG. 2) therein defined by the end edge 33 of the glue flap segment 18 and the surface 34 of the dust flap 21. i

In accordance with the invention, the right angular step 32 is eliminated and a bridge is formed between the upper surface 35 of the glue flap segment 18 and the upper surface 34 of the dust flap 21 by a solid fillet of thermoplastic material 36, as shown in FIGS. 1 and 2. More specifically, the fillet 36 initially has a generally right angular cross section, the hypotenuse of which extends between the upper surfaces of the glue flap segment l8 and dust flap 21, as best shown in FIG. 2. In accordance with the principles of the invention, it is this material to which an overlying sealing membrane 42 may be heat sealed during drumhead formation. It willbe appreciated that absent the fillet 36, it would be extremely difficult, if not impossible using conventional platen sealing techniques, to seal the membrane along the edges of the step, more specifically, along the vertical surfaces 33 of the glue flap segment 18.

In accordance with the principles of the invention, the fillet 36 is formed in situ, advantageously during the carton erection and filling. operations and after the carton tube hm been squared into a parallelepiped configuration and its end flaps are dust flaps outfolded into the position shown in FIG. 1. At this stage in carton manufacture, a daub of molten or at least spreadable hot melt material is placed at the vertical edge 33 of the glue fiap segment 18, and it is then spread along the step to form the fillet 36,, which fillet may extend from the carton edge 17 outward beyond the area of drumhead attachment. In the illustrated embodiment, the fillet is extended from the carton edge 17 to the end of the compound glue flap 31, however, it is only necessary for the fillet to intersect the area 40 of peripheral bonding of the membrane 42 to the outfolded flaps.

5 More specifically, and as shown in FIG. 3, after being squared 3 and placed on the carrier of the packaging machine, cartons are advanced continuously along a horizontal path into engagement with a switch A. Actuation of switch A energizes a solenoid B which fires an air cylinder C, which, in turn, momentarily opens a valve D to apply a quantityv of hot melt 36 on the trailing dust flap 21 through a nozzle E. 7

With continued advance of the cartons, the sealing membrane 42is applied and then is sealed, in tape form, to a group of cartons simultaneously by a group of heated sealing shoes F which move alongthe path'with the cartons and which are lowered into pressuredengagement with the outfolded flaps and upper ends of the cartons 10. An exemplary sealing mechanism is disclosed in more detail in Lense U.S. application SertNo. 835,008, filed June 20, 1969 and titled Packaging Machine With Continuous Motion Sealer."

As shown in FIG. 6, the lower or sealing surfaces of each sealing shoe F are especially contoured and define thecircumscribing sealing zones 40. A relieved area G of the shoe receives and presses against the glue'flap segment 18 overlying the dust flap 21, while the other embossing-sealing surfaces H of the shoe tend to press against the exposed surfaces of the dust flap 21, and theflaps 19, 20, 22. As an important aspect of the invention, a so-called peninsula or finger I (FIG. 6) extends into the relieved areaG and serves to cross-crush and to cross-score the glue flap portions 18', the dust flap portions 21', and the hot melt 36 at the step between the flaps l8 and 21 so as to form a dam 44 extending transversely of the dust flap and across the joint (see FIGS.4 and 5 Importantly, andas'shown in FIG. 5, the hot melt at the dam 44 is flattened by the finger I, thus changing the shape of the fillet of hot melt at the area of the dam and allowing the membrane 42 to be sealed to both the glue flap 18 and the dust flap 21 in'a common horizontal plane 41 defined by the surface of the platen 'finger l. Advantageously, the membrane 41 is secured to exposed portions of the single thickness flaps 19, 20, 21, 22 by embossed areas H of the sealing platen to form embossedsealed surfaces 46, while the membrane is secured to the com posite flap by unembossed portions 1 and G of the platen to form smooth-sealed surfaces 45 (H6. 5). As will be understood, this construction creates a barrier to leakage along the manufacturers joint and forms a new and improved drum-' head seal which is superior to those heretofore obtainable.

The four comers ofthe carton are, of course, included within the sealing zones 40. Extra'tightnessof the seal of the membrane to the comers may be effected by expanding the comer areas 43 or surfaces by crushing, controllably tearing, or otherwise re-forming the same. After the membrane is heat sealed to the flaps, the carton flaps 19-21 are infolded, as

shown in FIG. 6, to complete the carton.

lt shouldbe understood that the specific drumhead closure 7 and the method of efi'ecting the same herein illustrated and described are intended to be representative only, as certain changes may be made therein without departing from the clear teachings of the disclosure. Accordingly, reference should be made to the following appended claims in determining the full scope of the invention.

I claim:

1. In a parallelepiped carton having consecutively articulated first side, front, second side, and rear walls with said rear wall adhered to said first side wall by a glue flap articulated to said rear wall; said carton having first, front, second, and rear closing flaps articulatedto each of said first side, front, second side, and rear walls, respectively, and a glue flap segment articulated to said glue flap; said glue flap segment being adhered to said first flap and defining therewith a composite flap having a discrete step therein, an improved drumhead closure comprising i a a. thermoplastic fillet means disposed in and along step; b. said fillet means providing a bridging surface between the upper surface of said glue flap segment and the upper surface of said first flap;

'c. a heat scalable membrane tightly adhered about the said front flap, said second flap, and saidrear flap;

' d. said membrane being adhered by straight line-heat seals;

v e. a portion of said upper surface of said glue flap segment being crushed into the plane of the upper surface of said first flap along one of said heat seals f. whereby the end of said parallelepiped carton is sealed in an airtight and siftproof fashion. v

2. The carton of claim 1, in which a. said discrete step is generally right angular;

b. said fillet has a generally rectangular cross section in the region of hat sealing of the membrane to the glue flap and first flap.

3 The carton of claim 1, in which a. said fillet extends substantiallythe entire length of said v I composite flap. 4. A method of applying a drumhead membrane to the outfolded four flaps of carton, one of which flaps is a composite flap having a glue flap segment overlying an underlying flap portion-and defining therewith a discrete step, said methodcomprising the steps of:

a. depositing a molten thermoplastic fillet means in and along said step;

b. covering the outfolded four flaps with a heat scalable 5. The method of claim 4, in which steps (a) through (d) are effected during advance of the carton along a predetermined path by a packaging machine. 

1. In a parallelepiped carton having consecutively articulated first side, front, second side, and rear walls with said rear wall adhered to said first side wall by a glue flap articulated to said rear wall; said carton having first, front, second, and rear closing flaps articulated to each of said first side, front, second side, and rear walls, respectively, and a glue flap segment articulated to said glue flap; said glue flap segment being adhered to said first flap and defining therewith a composite flap having a discrete step therein, an improved drumhead closure comprising a. thermoplastic fillet means disposed in and along said step; b. said fillet means providing a bridging surface between the upper surface of said glue flap segment and the upper surface of said first flap; c. a heat sealable membrane tightly adhered about the periphery of the end of said carton at the edges thereof to said glue flap segment, said fillet means, the exposed portion of said first flap not underlying the glue flap segment, said front flap, said second flap, and said rear flap; d. said membrane being adhered by straight line heat seals; e. a portion of said upper surface of said glue flap segment being crushed into the plane of the upper surface of said first flap along one of said heat seals f. whereby the end of said parallelepiped carton is sealed in an airtight and siftproof fashion.
 2. The carton of claim 1, in which a. said discrete step is generally right angular; b. said fillet has a generally rectangular cross section in the region of hat sealing of the membrane to the glue flap and first flap.
 3. The carton of claim 1, in which a. said fillet extends substantially the entire length of said composite flap.
 4. A method of applying a drumhead membrane to the outfolded four flaps of carton, one of which flaps is a composite flap having a glue flap segment overlying an underlying flap portion and defining therewith a discrete step, said method comprising the steps of: a. depositing a molten thermoplastic fillet means in and along said step; b. covering the outfolded four flaps with a heat sealable membrane, c. applying heat and sealing pressure to said membrane and flaps along discrete linear zones; d. simultaneously crushing a portion of said glue flap into the plane of said underlying flap portion and flattening said fillet means in said zone at said step.
 5. The method of claim 4, in which steps (a) through (d) are effected during advance of the carton along a predetermined path by a packaging machine. 